In the conventional system (torque value method) the pre-load force is applied by a mounting process which shows torsion- and friction stresses at the nut and the bolt by torqueing them together. During this process the torqueing tool has to work against to moment of thread pitch and the friction at the thread on both laydown surfaces.
At the assembling process the thread friction, the head friction- and moment of thread pitch come all together. The thread- and moment of thread pitch can have a value of 90% of the final torque value.
The assembly pre load shows a high deviation based on the deviation of the friction values of the thread and under the head of the volt. The friction value by friction class B shows a deviation from 0,08 to 0,16, by these value the preload force can deviate of about 100%.
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